VIENNA (Reuters) - Iran failed to suspend uranium enrichment activity by February 21, ignoring a U.N. Security Council deadline to halt work the West fears could give Tehran an atomic weapon, the U.N.’s nuclear watchdog said on Thursday.

The International Atomic Energy Agency also said in a report that Iran had installed two cascades, or networks, of 164 centrifuges in its underground Natanz enrichment plant with another two cascades close to completion.

It said Iranian workers lowered into the plant an 8.7-ton container of uranium hexafluoride gas (UF-6) to prepare to start feeding centrifuges, which can enrich the material into fuel for power plants or, if refined to high levels, for bombs.

Iran’s defiance of a 60-day deadline set by the Council when it banned nuclear technology transfers to Iran on December 23 will expose Iran to wider sanctions over its atomic energy program, which the West fears is a front for assembling atom bombs.